Anti-government protests in Turkey have again turned violent after riot police fired tear gas and water cannons at the Gezi Park protesters in Istanbul.

Some of the protesters are believed to have shot at police personnel, injuring two during the violent riots, government sources said.

"Provocateurs have started using guns now. Two security force members have been injured. I think it is important to inform our public," said Istanbul governor Huseyin Avni Mutlu.

The night witnessed one of the worst clashes between the police and the demonstrators since the unrest began more than two weeks ago.

Although the protesters fled the park for a brief while, they came back lighting bonfires and placing barricades.

At least two dozen people have been injured during the recent evacuation which turned violent. Prime Minister Recep Tayyip Erdogan's government says none of the injuries are serious.

Mutlu said the skirmishes "lasted for a short time and did not cause any problems". He added: "This is not an intervention, it's an evacuation. Only small marginal groups remained in the park before the operation."

Scores of people have also participated in rallies in the Turkish capital Ankara.

Hours ahead of the police operation, Erdogan warned that there would be evacuation if the protesters remained defiant.

"We have our Istanbul rally tomorrow. I say it clearly: Taksim Square must be evacuated, otherwise this country's security forces know how to evacuate it," he said at a rally earlier.

For the moment, he has also stopped the redevelopment plans for Gezi Park, the triggering point of the protests. The plans await judicial approval.

"I'm addressing the well-intentioned [protesters]. The park belongs to the citizens of Istanbul. It's not the occupied land of illegal organisations. There is no point in staying at Gezi Park when there is a legal process," Erdogan said.

A similar police crackdown during the initial days of the unrest in Gezi Park set off a wave of protests against the government riding on anti-Erdogan sentiments.

"This is unbelievable. They had already taken out political banners and were reducing to a symbolic presence in the park," Koray Caliskan, a political scientist at Bosphorus University who was present in Gezi Park, told Reuters.